by Nigel Holmes

Created on: April 07, 2009

Contrary to the image portrayed in science fiction movies, the modern industrial robot is nothing more than a machine that moves a gripper through a preprogrammed path. This motion is achieved by a series of linked arms with a motor at each joint. Each motor is driven by a computer, which compares the current position to the programmed location, calculates the movement required, and commands each motor to move through a set angle at a predetermined speed.

Most robots have four to six axes of movement, although some do have more. Robots are produced in a wide range of sizes, from compact bench-top units that grip nothing more than a glue gun to huge machines that can lift an entire car, and are used in many different ways.

In the automobile industry the main uses are welding and paint spraying. The spot welding equipment used to assemble a vehicle body is bulky and heavy yet must be positioned precisely time after time to assure the structural rigidity of the car. This is a difficult task for a human, yet one a robot can perform over and over without making a mistake. In the same vein, it's very difficult for a human to achieve a perfect coating of paint every time, yet a robot, by virtue of its' ability to follow a path over and over without error, will produce a flawless finish every time. What's more, using a robot avoids the need for a human to work in the unpleasant environment of a spray booth.

Other uses of robots are machine loading and unloading and dispensing adhesives and sealants. Interestingly, few robots are used in vehicle assembly because the work is too complex and tolerance stack-ups mean that fine adjustment is sometimes needed to get parts to fit. An exception is the use of robots to mount wheels. A camera looks for the position of the wheel studs, then feeds this information to the robot which rotates the wheel to line it up prior to mounting.

Modern robots are exceptionally reliable machines with "Mean Time Before Failure" figures of twenty thousand hours or more. When problems do occur they tend to be with the grippers or due to changes in the environment such as parts not being presented in the right orientation.

This highlights one of the biggest weaknesses of industrial robots: they lack any ability to react to deviations from programmed conditions. For example, if a part is not placed in exactly the right position the robot will not find it. For this reason there is a growing move towards "vision-guidance" where cameras are used to provide 3D information on the location of parts or pallets.

There is no doubt that robots have replaced people in a number of roles. On the other hand they have also taken people out of hazardous working environments and have helped to improve the quality of our cars while making them more affordable than ever.

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